Bladed rotor



Dec.9,1947.

Driven: Al n Howard,

His Attorney Patented Dec. 9, 1947 BLADE!) ROTOR Alan Howard,Schenectady, N. Y., assignor to General Electric Company,

New York a.

a corporation of Application August 14, 1943, Serial No. 498,643 1Claim. (Cl. 253--39) The present invention relates to bladed rotors suchasare used in turbines. It finds especial utility in rotors -for gasturbines such as, for example, turbosuperchargers wherein the rotorsoperate at high speeds and are subjected to high temperatures at the rimand are strongly cooled at the web. It is this application of myinvention which I have elected to specifically illustrate and describe.It is to be understood, however, that this is only by way of example andthat my invention may be used whereverfound applicable in hightemperature, high speed rotors.

- The object of my invention is to provide an improved rotor of the typereferred to and for a consideration of what I believe to be novel and myinvention, attention is directed to the following specification and tothe claim appended thereto.

In the drawing, Fig. 1 is an end view of a part of a turbine wheelembodying my invention and Fig. 2 is a. sectional view taken on line 2-2of Fig. l.

Referring to the drawing, i indicates the hub, 2 the web, 3 the rim and4 the blades of a turbine wheel. In the present instance a shaft 5 isshown as bein formed integral with the hub.

According to my invention, I provide a wheel wherein the rim for thewheel, which rim carries the buckets, is formed from an alloy havinggood high temperature properties, particularly as regards strength, andthe web and hub are formed from an alloy having good low temperatureproperties, particularly as regards strength, the rim and web beingunited to each other by fused metal. In this connection, it is pointedout that in high' temperature turbines such as gas turbines receivingmotive fluid at temperatures well above 1000 F. it is customary tostrongly cool the web and hub portions of the bucket wheels by a blastof cooling air or other cooling medium 50 that they operate attemperatures relatively low compared to that at which the rim andbuckets operate. With such a cooling arrangement, the buckets are cooledby conduction of heat to the comparatively cooler web portion of thedisk. In such turbines, the temperature of the fluid entering thebuckets may be in the neighborhood of 1250 F., the temperature of thebuckets around 1200 the temperature of the rim portion 1150 F., whilethe central web portion of the bucket wheel is maintained somewherearound 600 or 700 F. by the cooling medium. According to my invention, Iutilize for the rim and for the web and hub alloys best suited for theoperating conditions met with in. each instance.

The high-temperature rim material may be any one of several known alloysof a type which show,

no allotropic transformation when heated and cooled and are nonmagnetic.The most common high-temperature alloys of this type are those knowngenerally in the metallurgical art as austenitics. It is desired to callattention however to the fact that this term has been generally, andsomewhat loosely, applied to many high-temperature alloys having thesame general characteristics as'the true austenitics, but having only avery few percent of iron, or in some cases no iron at all. One of these"non-ferrous austenitics" which may be used for the high-temperature rimhas the following composition:

Percent CO Ni 20 Cr 25 WC 5 1 I desire it to be understood that the termaustenitic" as used hereinafter is intended to include suchaustenitic-like alloys.

One suitable material for the hub and web is SAE 4140. steel. Another isan alloy comprising iron and about the given percentages of thefollowing metals:

In the illustrated embodiment of my invention,

I provide buckets having rectangular bucket cover sections 6 and havingbases which may be attached to the rim in any suitable manner, such asby welding, by dovetailed connections or the like.

In the present instance, the bases are shown as comprising a bottomplate 1, a neck 8 and a head 9, the plates 1. being rectangular andfitting against each other in .a completed wheel, and the necks 8 andheads 9 being located in suitable transverse slots formed in rim 3. Thusthere is provided a rim in the form of a ring to which the bases of thebuckets are fixed by dovetail connections, the rim being formed of asuitable high-temperature alloyv as pointed out above. The rim isattached to the web and hub by welding as is indicated at In in Fi 2. Itmay be attached to the web either before or after the blades has goodtensile strength and life at the elevated temperatures encountered ingas turbine operation. but unfortunately it is difiicult to forge. Inthe present state of the art it would be difllcult, if possible at all,to make an entire turbine disk, of the sizes needed for gas turbines,wholly of this material. Even if such a disk were fabricated, it wouldhave but a limited life because incapable of enduring for any length oftime the great temperature gradients from the central portion of the webto the rim which are encountered n .gas turbine service. Therefore, inorder to readily fabricate a rim portion which will have adequatestrength and life, it is desirable to keep the radial width of the hightemperature rim portion as small, as possible. and preferablysubstantially less than the radius of the combined hub and web portions.v 7

By my invention, I provide a rotor which is capable of beingmanufactured readily and which, due to the rim and the web and hub beingformed from materials suited particularly to the operating conditionsmet with, gives superior service.

bodiment thereof. burr desire to have i't'understood that the apparatusshown is only illustrativeand that the invention may be carried out byother means.

WhatI claim as new and desire to secure by tion. a web portionfabricated of a ferrous alloy In accordance with the provisions of thepatent material which is easily worked and has good strength propertiesat operating temperatures below 1000 F., an annular rim portion weldedto the outer circumference of the web portion, and an annular row ofbuckets secured to the rim portion, the rim portion being fabricated ofan austenitic material having good strength properties above 1000 F..and being of a radial width substantially less than the radius of thecombined hub and web portions.

ALAN HOWARD.

REFERENCES CITED The following references are file of this patent:

UNITED STATES PATENTS of record in the Number Name Date 2,058,479Lysholm Oct. 27, 1936 2,174,380 Doran Sept. 26, 1939

